The invention relates generally to welding techniques, and more particularly to improved processes for utilizing metal cored welding wire electrodes for enhanced performance, particularly in automated welding applications. The present disclosure is related to a previously filed provisional application 61/503,955, entitled Metal Cored Welding Method and System, filed by Summers et al. on Jul. 1, 2011, which is hereby incorporated into the present disclosure by reference.
A range of techniques have been developed for joining workpieces by welding operations. These include diverse processes and materials, with most modern processes involving arcs developed between a consumable or non-consumable electrode and the workpieces. The processes are often grouped in such categories as constant current processes, constant voltage processes, pulsed processes, and so forth. However, further divisions between these are common, particularly in processes that consume an electrode to add filler metal to the weld. In virtually all such cases, the process selected is highly linked to the filler material and its form, with certain processes exclusively utilizing a particular type of electrode. For example, certain types of metal inert gas (MIG) welding processes, which form part of larger groups sometimes referred to as gas metal arc welding (GMAW) and flux cored arc welding (FCAW).
In GMAW welding, an electrode in the form of a wire is consumed by the progressing weld pool, melted by the heat of an arc between the electrode wire and the workpiece. The wire is continuously fed from a spool through welding gun where a charge is imparted to the wire to create the arc. The electrode configurations used in these processes are often referred to as either solid, flux cored, or metal cored wire. Each type is considered to have distinct advantages and disadvantages over the others, and careful adjustments to the welding process and weld settings may be required to optimize their performance. For example, solid wire, while less expensive than the other types, is typically used with inert shielding gases, which can be relatively expensive. Flux cored wires may not require separate shielding gas feeds, but are more expensive than solid wires. Metal cored wires do require shielding gas, but these may be adjusted to mixes that are sometimes less expensive than those required for solid wires. Although metal cored wires offer distinct advantages over the other electrode types, their adoption has not been as widespread as solid wires.
All three of these electrode types may be used with different transfer modes, referring to the mechanical and electromechanical phenomena of moving metal from the electrode tip to the progressing weld bead. A number of such transfer modes exist, such as short circuit transfer, globular transfer, spray transfer, and pulsed spray transfer. In practice, transfer physics may appear as a hybrid of these, and the actual material transfer may transition between them during welding, although the process and electrode are often selected to maintain a certain transfer mode.
While it has long been realized that metal cored wire electrodes offer benefits that are advantageous over their solid and flux cored counterparts for many reasons, improvements in processes are needed that can enhance their performance and adoption.